FIG. 1 is a perspective view of the seat cushion showing our novel ornamental design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational view of one side thereof, the opposite side being a mirror image;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a top plan view of the seat cushion with an inflatable cushion insert therein shown in phantom;

FIG. 8 is a side elevation view thereof;

FIG. 9 is a front elevational view thereof; and,

FIG. 10 is a rear elevational view thereof.

The phantom lines showing the inflatable cushion insert form no part of the claimed design.